Among the various types of apparatus used to remove impurities and contaminants from water is an apparatus which employs the technique commonly called electrodeionization. One example of an apparatus of this type is manufactured by the Millipore Corporation of Bedford, Massachusetts. In an apparatus of this type, liquid to be purified is passed through depleting compartments containing mixed anion and cation exchange resin beads while a second liquid is passed through concentrating compartments free of ion exchange resin beads. Ions under the influence of a direct current potential, pass from the depleting compartments into the concentrating compartments through ion permeable membranes. A more detailed description of this apparatus may be found in co-pending application Ser. No. 762,804, filed Aug. 2, 1985 now U.S. Pat. No 4,632,745, the teachings of which are incorporated herein by reference.
One problem often encountered in electrodeionization apparatus is a pressure drop across the compartments believed to be caused by fouling of the ion exchange beads and concentrating compartment screens by agglomerations of organic contaminants. In the past, alkaline brine has often been used to alleviate this fouling but has not been as effective as desired.